well because of the movable drive and driven faces it really doesn't matter what size belt you put in it as long as it's close to the same length. i bought one from advance auto parts and it works fucking awesome. just bring your old belt up there and try to match it with some they have. you'll probably want it a few millimeters thicker though.
there's some cool shit you can do with it if you experiment with different lengths and thicknesses of the belts due to the variator weights
I figure since the auto choke is basically just a thermostat then it won't matter if you just plug it up if you plan on getting a new carb with it's on choke. right? maybe?